plant propagation pls 3221/5222 - university of...

1

Plant Propagation PLS 3221/5222

Dr. Sandra WilsonDr. Mack Thetford

Chapters 9 & 10

Principles and Techniques of Cutting Propagation

Part 1

2

Chapters 9 & 10

Principles and Techniques of

Propagation by Cuttings

Cutting propagation = The clonalmultiplication of plants with propagulesof stems, leaves, or roots.

Chapters 9-10 ObjectivesStudent should be able to:

1. Describe different types of cuttings.– Describe adventitious root and bud formation for a variety of cutting types

2. Explain how hormonal control affects root and bud formation.– Classification of plant rooting response to growth regulators

– Understand how stock plants can be manipulated to maximize adventitious root formation

3. Understand the biochemical basis for adventitious root formation.– Endogenous rooting inhibitors

– Rooting co‐Factors (Auxin synergists)

3


4. Describe recent advances in asexual propagation.

5. Discuss the management and manipulation of stock plants to maximize cutting production and root formation.

– Selection and maintenance of propagation material

– Rejuvenation of stock plants

– Manipulating the environmental conditions and physiological status of the stock plant

– Selection of cuttings from stock plants


6. Discuss how cuttings are prepared for propagation and treatment of cuttings to improve rooting success.

– Storage

– Rooting Hormones (auxins)

– Cutting nutrition

– Wounding

4


7. Describe how the propagation environment is managed and how to manipulate the rooting environment to improve rooting of cuttings.

– Water relations – humidity control

– Temperature

– Light (quality, quantity and photoperiod)

8. Describe how cuttings are managed after rooting.

9. Identify management practices utilized in propagation.

• Commercial woody and herbaceous plant production (Lake Brantley Plant Co.)

• Discussions about rooting indices and hormone application for cuttings (Drs. Davies & Thetford)

• Propagation by Cuttings Lecture (Dr. Davies)

Dr. Fred Davies is a professor of Horticultural Sciences and Plant Physiology at Texas A&M University.He teaches, does research in propagation and was a Fulbright Senior Fellow to Mexico and Peru.

Dr. Fred Davies

5

• Mechanization of propagation and tour of facility (Hatchett Creek Farm, Gainesville, FL)

• Discussions about rooted cutting production scheduling and stock plants with Dr. Rick Schoellhorn and George Griffith

Dr. Schoellhorn was an associate professor of environmental horticulture and a statewide extension specialist for commercial floriculture at the University of Florida at the time of the presentation. Presently Dr. Schoellhorn is with private industry.

Dr. Rick Schoellhorn

• Stock Plant Management- An introduction to the cutting propagation industry

• Stock Plant Management – Managing the propagation environment to maximize rooting

Dr. Gibson was a commercial floriculture extension specialist at the University of Florida working to develop production and management solutions for the ornamental plant industry at the time of this presentation.

Dr. James Gibson

6

1. Descriptive Observations of adventitious root and bud formation

• Types of cuttings

–Stem cutting

–Leaf‐bud cutting • (single‐eye cutting)

–Root cutting

–Leaf cutting

Dedifferentiation‐

• The capability of previously developed, differentiated cells to initiate cell divisions and form a new meristematic growing point.

7

Adventitious rootformation

Preformed roots

(latent root initials)

Preformedroot initials

Preformed root initials and root primordia develop naturally on stems while they are still attached to the parent plant.

Adventitious roots arising from preformed root initials

Campsis radicans

8

Adventitious root formation

Wound‐induced roots

Wound‐induced roots develop only after the cutting is made, in response to wounding in preparing the cuttings.

These roots are formed de novo (anew)

Copyright ©2011, 2002, 1997, 1990, 1983, 1975, 1968, 1959 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.

Hartmann and Kester’s Plant Propagation Principles and Practices 8eHudson Hartman, Dale Kester, Fred Davies and Robert Geneve

DESCRIPTIVE OBSERVATIONS OF ADVENTITIOUS ROOT AND BUD (AND SHOOT) FORMATION

Figure 9–3 Leaf bud cuttings of Ficus pumila with (a) unrooted cutting, (b) wound induced, de novo and (c) preformed adventitious roots. (d) Philodendron cutting with preformed adventitious root from node.

9

Wound response

Step 1. Protection from desiccation and pathogens.

• the outer injured cells die,• a necrotic plate forms,• the wound is sealed with a corky material (suberin), and

• xylem may plug with gum.

Wound response

Step 2. Wound periderm formation.

• Living cells behind the plate begin to divide after a few days.

• A layer of parenchyma cells form callus.• Wound periderm= a mass of callus cells that forms a

protective layer behind the wounded surface of a cutting.

• Parenchyma cells= the basic cells from which all other differentiated cells and tissues are derived.

10

Wound response

Step 3. Adventitious root formation.

• Cells in the vascular cambium region and phloem begin to divide and initiate de novo adventitious root formation.

4 Stages of adventitious root formation

ROOT INITIATION1. Dedifferentiation of specific

differentiated cells2. Formation of root initials3. Development of root primordiaROOT GROWTH4. Growth and emergence of root

primordia

11

Anatomical origin ofWound induced roots

Herbaceous plants – usually just outside and between the vascular bundles.

• Tomato phloem parenchyma

• Pumpkin phloem parenchyma

• Mung been phloem parenchyma

• Crassula epidermis

• Coleus pericycle

Dicot Stem

www.botany.uwc.ac.za/ecotree/ trunk/VasBundle.htm

12

Dicotstem

vascularbundle

www.botany.uwc.ac.za/ecotree/ trunk/VasBundle.htm

Anatomical origin of wound induced roots

• Woody perennial plants – usually from living parenchyma cells, in the young, secondary phloem, but sometimes in vascular rays, cambium, phloem, callus, or lenticels.

13




Stem structure & rooting ability

EpidermisSclerenchyma RingPhloemCambiumXylemRayOrigin of Root Initials

14

Root formation

• Direct root formation ‐ Cells in close proximity to the vascular system.(generally more easy to root species)

• Indirect root formation – nondirected cell division (callus formation) precedes cell differentiation and vascular strand formation. (generally more difficult to root species)

Cutting Taken

Direct Root Formation

Competent

Root Forming Cells:

Potential Root Initiation Sites

Indirect Root Formation

Cell division

Cell differentiation

Vascular Strand formation

Induced Competent

Root Forming Cells:

Potential Root Initiation Sites

Root Initials

Root Primordium

Root Emergence

15




Figure 9–11 Flow diagram of adventitious root formation through direct (cells in close proximity to vascular system—i.e., generally more easyto- root species) and indirect model (interim period of undifferentiated cell division—i.e., generally more difficult-to-root species). When a potential root initiation site is already present the initial cell divisions lead to root production in situ. When a site is not present, alternative routes leading to the creation of a site are shown. Rooting does not always occur. Modified from Lovell and White (185) and Geneve (98).

Stem Cuttings

16

Leaf Cuttings ‐ Adventitiousbud & root formation

Preformed primary meristems‐

directly descendent from embryonic cells that have never ceased to be involved in meristematic activity

Wound‐induced secondary meristems‐

new meristematic zones (de novo) resulting from dedifferentiation of cells of a differentiated tissue system

Leaf Cuttings –preformed, primary meristems

• New plants develop from a latent primary meristem – from cells that have not fully differentiated.

Rudimentary leavesStem (w/intact bud)Root primordiaFoot

Rudimentary leavesStem (w/intact bud)Root primordiaFoot

Leaf blade & margin

17



TYPES OF CUTTINGS

Figure 10–19 (a) The piggy-back plant (Tolmiea menziesii) forms plantlets (arrows) on its leaves. The new plants arise at the junction of the leaf blade and petiole. The plant is propagated by leaf cuttings. (b) Leaf cuttings of Bryophyllum crenatodaigremontianum and (c) Bryophyllum daigremontianum. New plantlets develop from foliar “embryos” in the notches at the margin of the leaf (arrows). Leaves are partially covered or pegged down to hold the leaf margin in close contact with the rooting medium.

Leaf Cuttings –Wound‐induced, secondary meristems

• New plants may develop from secondary meristems arising from differentiated cells at the base of the leaf blade or petiole as a result of wounding.

• Root initiation and development are independent of adventitious bud and shoot development.

18

Leaf Cuttings –Wound‐induced,

secondarymeristems

• African violet

• Begonia

• Snake plant



TYPES OF CUTTINGS

Figure 10–18 Leaf cuttings of Sansevieria. (a) Leaf blade with adventitious roots. (b and c) New plant with shoots and adventitious shoots and roots. The original leaf cutting does not become a part of the new plant.

19

Callus formation

Root organogenesis

• Primarily from the vascular cambium

• Cells of the cortex and pith may contribute

Shoot organogenesis

• disorganized calli

Leaf Cuttings –Adventitious bud formation

• The limiting factor in leaf cutting propagation is generally the formation of adventitious buds, not adventitious roots.

• In some plants, the cutting must include a portion of the stem containing an axillary bud (a leaf‐bud cutting).

20

Leaf bud cuttings



TYPES OF CUTTINGS

Figure 10–15 Leaf bud cutting or single eye cuttings—more propagules can be produced than with larger shoot cuttings. (a) Ficus pumila and (b) several leafbud cuttings of pothos directly stuck for rooting.

21

Leaf‐Bud cuttings

• Single‐eye or single‐node cuttings

• Consist of a leaf blade, petiole , and a short piece of stem with the attached axillary bud.

• Only adventitious roots need to form.

Leaf Cuttings

• Adventitious buds, shoots, and roots form at the base of the leaf cutting.

• The original leaf does not become part of the new plant.

22



TYPES OF CUTTINGS

Figure 10–17 Various types of leaf cuttings with new plantlets developing (arrows): (a) African violet, (b) Cape primrose (Streptocarpus), (c) Begonia leaf pieces, (d) Begonia whole leaf cut on main veins, and (e) Sedum.

23

Root cuttings

Root Cuttings –Adventitious bud and root formation

• A new shoot system and a new root system must be regenerated.

• Generally, adventitious shoots followed by roots, often from the base of the new shoot rather than from the original root piece.

24

Root Cuttings –Adventitious bud formation

• Young roots–Pericycle – near the vascular cambium

• Old roots–Callus‐like growth from the phellogen

–Callus‐like proliferation from vascular ray tissue

Root cuttings –Adventitious root formation

• New roots may not be adventitious

–May develop from latent lateral root initials contained in the root piece or attached lateral roots

• Adventitious

–Observed to arise in the region of the vascular cambium

25



TYPES OF CUTTINGS

Figure 10–22 Propagation by root cuttings with (a) sassafras and (b) blackberry. New adventitious shoots (arrows) and roots form from the root cutting.

Polarity in Cuttings

Distal

Proximal

Proximal

Distal

26




• Root Cuttings—Adventitious Bud (and Shoot) and Root Formation

• Polarity and Organ Formation in Cuttings

Figure 9–16 Polarity of root regeneration in grape hardwood cuttings. Cuttings at left were placed for rooting in an inverted position, but roots still developed from the morphologically basal (proximal) end. Cuttings at right were placed for rooting in the normal, upright orientation with roots forming at the basal end.

Correlative Effects:How Hormonal Control Affects Adventitious Root

and Bud (Shoot) Formation

• The control of one organ over the development of another, which is mediated by phytohormones.

• Auxin produced from axillary buds is transported basipetally down the shoot and is important in subsequent root formation at the base of a cutting.

27

Bud Effects on Rooting

For root initiation, the presence of an actively growing shoot tip (or lateral bud) is necessary during the first three or four days after the cuttings are made.

If hardwood, deciduous cuttings are taken in midwinter when the buds are in the rest period, they have either no effect or can inhibit rooting.

Leaf Effects on Rooting

The presence of leaves on cuttings exerts a strong stimulating influence on rooting

• Carbohydrates translocated from the leaves are important for root development

• Leaves also produce auxin that is translocated to the base of the cutting

28



CORRELATIVE EFFECTS: HOW HORMONAL CONTROL AFFECTS ADVENTITIOUS ROOT AND BUD (AND SHOOT) FORMATION

Figure 9–17 Effect of leaves, buds, and applied auxin on adventitious root formation in leafy ‘Old Home’ pear cuttings. Top: Cuttings treated with auxin (indolebutyric acid at 4,000 ppm for five seconds). Bottom: Untreated cuttings. Left to right: with leaves; leaves removed; buds removed; one-fourth natural leaf area. Courtesy W. Chantarotwong.

Chapters 9 & 10

The Biochemical Basis for Adventitious Root Formation

29

The Biochemical Basis for Adventitious Root Formation

• Rooting inhibitors – endogenous chemical inhibitors which retard rooting.

• Rooting co‐factors – naturally occurring substances that act synergistically with auxin in promoting rooting.

Adventitious root production. Phase 1. Induction

Auxin+ soluble

carbohydrates

Injury effect

Accumulation of“auxin protectors” Low IAA

oxidase activity

Auxinaccumulation

Accumulation of phenolics

30

Adventitious root production. Phase 2. Early Initiation

Cell Division

σ - diphenols

Borate

•Inhibited by gibberellin or cytokinin supplied at high concentration•Enhanced by high concentration of supplied ABA

Adventitious root production.Phase 3. Late Initiation

Complexformation

Enhanced by supply of ethylene.Inhibited by lack of borate or high auxinconcentration.

Organization of root primordium

Ethylene

Diminished auxin

Enhanced IAA oxidase

31

Adventitious root production.Phase 4. Growth and differentiation

Growth and differentiation



THE BIOCHEMICAL BASIS FOR ADVENTITIOUS ROOT FORMATION

Figure 9–19 Hypothesized scheme of Jarvis (157) which proposes the role of phenolics, IAA oxidase/peroxidase, borate, and phytohormones in the four developmental stages of adventitious root production.

32

Chapters 9 & 10

Plant Growth SubstancesHormonal controls on rooting

Hormonal controls on rooting

• Auxin

• Cytikinin

• Gibberellin

• Ethylene

• Abscisic acid

• Ancillary compounds

–Growth retardants/inhibitors, polyamines, and phenolics

33

Auxins

Auxin is required for initiation of adventitious roots on stems, and it has been shown that divisions of the first root initial cells are dependent upon either applied or endogenous auxin.

Auxins ‐naturally occurring compounds

Indole‐3‐acetic acid • Considerable auxin activity

• Easily metabolized by the plant

Indole‐3‐butyric acid• More effective than IAA for rooting

• Recently (early 1990’s) shown to be a naturally occurring substance in plants.

34

Auxin – Synthetic compounds

α‐naphthalene acetic acid• More effective than IAA for rooting

See your text for a partial list of Commercial rooting compounds, sources, formulations, and ingredients.

Rooting Chemicals, formulations and carriers

• IBA is the best auxin for general use

– nontoxic to plants over a wide concentration range

– effective in promoting rooting of a large number of plant species

– a relatively stable compound as a powder or liquid

• IBA may be toxic to softwood cuttings of some species

35

Indole-3-Acetic AcidIAA Indole-3-butyric Acid

IBA

Movement of Auxinin cuttings

• Natural auxin moves from the apex to base.

• When applied to the base of the cutting it is absorbed and distributed throughout the cutting within 24 hours.

36

Cytokinins

Cytokinins have the greatest effect on initiating buds and shoots from leaf cuttings and in tissue culture systems

• Zeatin

• Zeatin riboside

• Kinetin

• Isopentenyladenin (2iP)

• Thidiazuron (TDZ)

• Benzyladenine (BA or BAP)

Gibberellins

• At relatively high concentrations they have consistently inhibited adventitious root formation.

• Gibberellins have a function in regulating nucleic acid and protein synthesis and may suppress root initiation by interfering with these process.

37

Ethylene

• Ethylene can enhance, reduce, or have no effect on adventitious root formation.

– causes root formation on stem and leaf tissue

– causes development of preexisting latent roots on stems

Abscisic Acid (ABA)

• ABA is important to rooting since it:

–Antagonizes the effects of gibberellins and cytokinins, both of which can inhibit rooting

– Influences the ability of cuttings to withstand water stress during propagation

38

Growth Retardants

• Growth retardants have been used to enhance rooting based on the rationale that they..

–Antagonize GA biosynthesis or activity

–Reduce shoot growth, resulting in more assimilates at the cutting bases

Classification of Plant Rooting Response to Growth Regulators

• Easy to Root –plants that have all the essential endogenous substances plus auxin.

– When cuttings are made and placed under proper environmental conditions, rapid root formation occurs.

– Auxin may enhance rooting, but is generally not required.

39


• Moderately Easy to Root ‐

plants in which the essential endogenous substances are present, but auxin in limiting.

–Auxin is needed to enhance rooting.


• Recalcitrant (difficult to root) – plants in which an essential endogenous substance is limiting or the plant lacks the cell sensitivity to respond to these substances, even though natural auxin may or may not be present in abundance.– Auxin application provides little or no enhancement of rooting.

40

Chapters 9 & 10

Management and manipulationof stock plants to maximize

cutting production and root formation.



MANAGEMENT OF STOCK PLANTS TO MAXIMIZE CUTTING PROPAGATION• Selection and Maintenance of Stock Plants for Cutting

Propagation• Rejuvenation of Stock Plants

– Inducing Rejuvenation

• Manipulating the Environmental Conditions and Physiological Status of the Stock Plant– Water Status– Temperature– Light– Stock Plant Etiolation– Girdling– Carbon Dioxide Enrichment– Carbohydrates– Managing Carbohydrate/Nitrogen Levels of Stock Plants

41

Management of Stock Plants to maximize cutting propagation

• Selection and Maintenance of Stock plants for cutting propagation

– Selection of easy to root source material (juvenile)

–Maintenance of stock plants in the juvenile/transitional growth phase

–Rejuvenation of stock plant material

Stock plant manipulation

Pruning may be used to:

• Maintain juvenility

• Shape plants for easier and faster cutting collection

• Increase cutting production

• Alter timing of growth flushes

• Reduce occurrence of reproductive shoots

42

Pruning

• Modified stooling

– Severely cutting back to the base but not mounding with soil as with traditional stooling.

• Pruning

– May range from severe pruning to normal removal of cuttings from the stock

Pruning• Hedging

?

43

Serial Propagation

Annual harvesting and rooting of cuttings from previously rooted containerized plants in production blocks.

A CB

Rejuvenation of Stock Plants

• In difficult to root plants, the ease of adventitious root formation declines with the age of parent stock.

Juvenile to mature

• Ontogenetic change

• Phase change

• Meristem aging

44

Rejuvenation of Stock Plants



MANAGEMENT OF STOCK PLANTS TO MAXIMIZE CUTTING PROPAGATION

Figure 9–25 Scheme for rejuvenation techniques used in serial graftage of ten-year-old Eucalyptus xtrabutii onto juvenile seedling understock. Six serial grafts (S1 to S6) were needed before mature grafted scions could be used as cuttings and rooted.

plant propagation pls 3221/5222 - university of...

Documents